JavaScript help in custtomizing a free template

hey guys..
this the first time 4 me..

and i'd like to join this great effort.. and enjoy exchanging my knowledge with you...

to be honest, M a very good PHP programmer .. and always design ma own websites in my way ..

but, here there are a professional designs.

So.. i decided to use a template for ma new task..
and i did choose this one:
https://freewebsitetemplates.com/preview/architecture2/


and here i've a q:
what z the best way to extend the menu.. "black menu"
i.e if i want to add a sub menu for "services" in the same design ..
how shall i do that....




a great thx 4 u all ...

 

thx dear,
I already did t ma self ..
thx 4 ur efforts ..


Regards.